Signaling system



July 26, 1932. 5, BROWN 1,868,691

SIGNALING SYSTEM Filed Oct. 26. 1929 INVENTOR flr'c/n'ba/a 5. Brown Y ATTORNEY Patented July 26, 1932 UNITED STATES PATENT OFFICE ARCHIBALD S. BROWN, OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL THE- GRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, .A. CORPORATION OF CALI- FORNIA.

SIGNALING SYSTEM Application filed October 26, 1929. Serial No. 402,774.

This invention relates generally to relay systems and has particular application to radio telegraph transmitting systems.

The specific object underlying the invention is to increase the rapidity of operation of a telegraph repeating relay without subjecting the relay winding to excessive current for long enough time to overheat it.

This is accomplished by inserting, as a major impedance element in the operating circuit of the repeating relay, a tungsten filament lamp, which has a relatively low resistance when cold and permits a large initial rush of current through the relay winding, but which has suflicient resistance when hot to limit the current to a safe value.

The drawing discloses a schematic circuit of a carrier telegraph system for generating continuous oscillations in response to closure of a telegraph key. The oscillation circuit includes a three electrode vacuum tube 10, having a cathode, grid, and anode. The input circuit of tube 10 includes an inductance 14 and the contacts 23 of a keying relay 80, and the output circuit thereof includes an inductance 16 shunted by a tuning condenser 17. A. load circuit 19, which may be an antenna or a transmission line, is coupled to inductance 16, by inductance 21.

The circuit described is designed for operation at short waves at which suflicient energy is transferred from the output circuit to the input circuit through the grid-anode capacity of the tubes to cause continuous oscillations whenever contacts 23 are closed.

The keying circuit for closing contacts 23 includes a key 24, a tungsten filament lamp 44, relay winding 30, and battery 26 connected in series. A control circuit of this type is desirable as it permits placing the contacts 23 close to inductance 14 and tube 10, while having key 24 at a remote point more convenient to the operator. With such a system of control it is desirable that relay 23 operate quickly in response to a closure of key 24. Since, due to the heavy insulation and current carrying requirements of the contacts, the relay is sometimes of comparatively massive construction, a heavy initial surge of current is necessary to obtain the desired quick operation. To obtain a heavy current the resistance of the relay winding is made very low and a tungsten filament lamp 44 is inserted in the circuit. As is well known, the resistivity of tungsten when heated to incandescence is several times as great as that of cold tungsten. The lamp 44 therefore permits a large initial surge of current and thereafter, due to its increased resistance when heated, limits the current in the circuit to a safe value. Although it is preferred to utilize a tungsten filament lamp, other resistance devices having large, positive, temperature-resistivity coefiicients may be substituted therefor, and the invention is limited in this respect only to the extent indicated in the claims.

I claim:

1. In a relay system, a relay, a source of current, a resistance element having a positive temperature coefficient, and a keying device, all connected in series, said resistance element being so proportioned relative to the total circuit resistance as to be heated, in response to closure of said contact means, to a temperature at which its resistance constitutes a major proportion of the total circuit resistance.

2. In a relay system, a relay, and an operating circuit therefor including a source of current, a keying device, and a current limiting resistance element comprising a lamp having a positive temperature-resistivity coeflicient.

3. In a relay system, a telegraph repeating relay and an operating circuit therefor including a source of current, a keying device, and a current limiting resistor comprising a tungsten filament lamp, said lamp being adapted to be heated by the normal current in said circuit to a temperature at which its resistance is greatly increased.

4. In a relay system, a series circuit including a relay, a source of current, a keying device, and means for limiting the steadystate current in said circuit comprising a resistance element having a large positive, temperature-resistivity coefficient, which element, when cold has a resistance low as compared to the impedance of the remainder of the circuit but which heats in response to current flowing therethrough to a temperature at which its resistance is large relative to the resistance of the remainder of the circuit.

In testimony whereof, I have hereunto set my hand.

ARCHIBALD S. BROWN. 

